1. Field of the Invention
The present invention relates to a conveyor apparatus, particularly for advancing rounded can bodies into a processing station from a station in which the can bodies assume a temporary position of rest with respect to their longitudinal axes. The device includes two synchronously driven, successively disposed advancing arrangements, each being equipped with at least one endless pulling (conveying) mechanism with dogs. Each pulling mechanism includes a flight facing the can bodies and extending parallel to their transporting direction. The flight extends between an upstream and a downstream guide wheel. The upstream disposed first advancing arrangement is operated at a uniform circumferential velocity. The dogs of the first advancing arrangement are arranged perpendicularly to the plane of travel of the pulling mechanism.
2. Discussion of the Prior Art
German Patent No. 2,748,910 (which corresponds to U.S. Pat. No. 4,162,382) discloses a transport device of the above-outlined type for use with an electrical resistance welding machine. The constant transporting speed of the first advancing device is generally higher than the processing (welding) speed. When the dogs of the first advancing arrangement impact on the stationary can body, the edge of the can body may be deformed or damaged by the theoretically infinitely high acceleration. To prevent this damage, the dogs are articulated to a chain as extending fingers thereof. This arrangement provides a certain resiliency, thereby damping the shock of the dog impacting on the can body. However, despite the resiliency of the dogs, in practice the can bodies are accelerated from zero to the full transporting speed by a jerky or jolting motion over a very short path which is in the order of magnitude of one or a few millimeters. This means that very high reaction forces are generated at the edge of the can body. These acceleration and reaction forces increase with the output of the device (that is, the number of can bodies processed per minute) and with the transporting speed so that an increase in the output can result in damage to the edges of the can bodies in spite of the resilient fingers.
In order for the transfer of the can bodies to take place from the first advancing arrangement operated at a higher circumferential velocity to the second advancing arrangement operated at a lower circumferential velocity without the disadvantageous jolts, German Patent No. 2,748,910 discloses providing the second advancing arrangement with pivotal pawls which are actuated by the outline of a guide rail.
German Patent No. 2,820,188 (which corresponds to U.S. Pat. No. 4,417,117) discloses a transporting device having two successively arranged endless chains, each being equipped with dogs. The chains are accelerated by means of a stepping gear assembly from a resting position to a speed around 200 m/min and then are decelerated again to a standstill. The entire velocity cycle is approximately sinusoidal. While in this prior art device the rounded can body is moved smoothly due to the gradual acceleration, and thus the edges of the can bodies are not likely to be damaged, the output of the transporting device cannot be significantly increased, because of the masses (such as the transporting chain, the dogs, the chain wheels and the gear components) which must be accelerated.
German Offenlegungsschrift (non-examined published patent application) No. 3,205,177 discloses a drive device for assembly pallets in transfer tracks in which the preliminary end position of a pallet is determined by the carrier of a first circulating chain at the rear reversal point, and the resumption of the movement of the pallet after the halt is effected by the carrier of a second chain at the front reversal point.
German Auslegeschrift (examined published application) No. 2,323,225 discloses a chain advancing mechanism where blank stacks are positioned against a stop by means of vertically arranged transporting fingers of a rotating chain drive arrangement at the rear deflection point.
German Patent No. 899,765 discloses a transporting device for container handling machines where the containers are moved at a sinusoidal velocity between two plate or belt conveyors by means of transporting fingers disposed at a rotating disc wheel.